The invention relates to liquid crystal displays and fabrication methods thereof, and more particularly, to polymer dispersed liquid crystal (PDLC) displays and fabrication methods thereof.
Among flat panel displays, liquid crystal displays (LCDs) exhibit characteristics of light weight, low power consumption, and good outdoor reliability, and are therefore widely applied in portable computers, notebooks, mobile phones, and personal digital assistances (PDAs). Conventional twisted nematic mode LCDs are disadvantageous due to their small viewing angle. Some proposed LCDs, such as, in-plane switching mode LCD (IPS-LCD) or multi-domain vertical alignment LCD (MVA-LCD) attempt to improve the viewing characteristics of conventional LCDs.
Conventional MVA-LCDs, however, possess less transparency than TN mode LCDs. Moreover, conventional MVA-LCDs image sticking may occur in display over a long period of time. U.S. Pat. No. 6,781,665, the entirety of which is hereby incorporated by reference, discloses a method for fabricating a polymer dispersed liquid crystal (PDLC) display. The polymer dispersed liquid crystal (PDLC) display is formed by mixing liquid crystal and monomer and radiating UV thereon with a bias. Polymers dispersed in liquid crystal can help liquid crystal recovery, thereby reducing imaging sticking.
FIG. 1 is a schematic view of a conventional method for fabricating a polymer dispersed liquid crystal display. A liquid crystal display panel is disposed in an ultra-violet light irradiation chamber 32. A power supply 30 applies a bias between an upper electrode 34 and a lower electrode 36. A liquid crystal layer 38 between the upper electrode 34 and the lower electrode 36 comprises a mixture of liquid crystal and monomer. When the liquid display panel is irradiated by UV light, the monomer is polymerized to form a continuous network. Moreover, during polymerization, the orientation of the liquid crystal becomes more consistent with the polymer.
FIG. 2 is a cross section of a conventional polymer dispersed liquid crystal display. After an irradiating or a heating process, monomers in the liquid crystal layer 38 between upper substrate 10 and lower substrate 20 are polymerized into polymer structures 13. Polymer structures 13 are formed adjacent to alignment layers 46a and 46b. Polymer structures 13 can aid in liquid crystal recovery, thereby reducing image sticking.
U.S. Pat. No. 6,014,194, the entirety of which is hereby incorporated by reference, discloses a polymer dispersed liquid crystal (PDLC) display. Monomers are added into liquid crystal. The mixture of monomers and liquid crystals in each of red, green, and blue color pixels are separately polymerized with UV irradiation under different biases, thereby creating a different polymer structure in each pixel.